In the interests of the environment, and to comply with increasingly stringent regulatory demands, it is desirable to increase the amount of alternative fuels used in automotive fuel formulations.
Biofuels are combustible fuels derived from biological sources, which result in a reduction in “well-to-wheels” (i.e. from source to combustion) greenhouse gas emissions. In gasoline fuels for use in spark ignition (petrol) engines, the most common biofuels are biologically-derived alcohols, in particular ethanol.
As a result of recent legislation, European and North American gasoline transportation fuels contain 10% v/v of ethanol (i.e. so-called “E10” fuels). The Renewable Fuel Standard (RFS) in the US requires 10% v/v biofuel in all gasoline grades, increasing to 20% v/v in 2022. Further, the European Union's Renewable Energy Directive (RED) will require 10% of all energy used in transportation to be renewable by 2020.
E10 fuels are currently available in a number of markets: they are compatible with existing fuel specifications, vehicle technology and distribution systems. The future availability of cellulosic ethanol may drive a transition to higher concentration ethanol blends in the future. However, E10 gasoline alone will not be sufficient to meet the requirements of the RED and RFS.
Whilst it would be desirable to be able to increase yet further the proportions of fuels from alternative sources, this is likely to be less than straightforward to achieve. It is in theory possible to run existing vehicle engines on E15 fuels (fuels containing 15% v/v ethanol), but a waiver of existing legislation would be necessary in order to do so. Meanwhile the use of fuels with higher ethanol contents would require specially adapted engines, which would increase supply chain complexity and also lower fuel economy. Although there is recognition from engine manufacturers that E20 fuels may be required in the future, the relevant regulations provide no incentive for mutually compatible vehicles and fuels.
Other so-called alternative fuels, for example biogas, can be derived completely from biological sources, but again can only be used in modified engines and are not well suited to existing fuel distribution systems.
It is known to produce liquid hydrocarbon fuel components from biomass, for instance using an aqueous phase reforming (APR) process such as is described in US20110257416. However, such components still need to be blended with conventional, petroleum-derived gasoline fuel components in order to achieve an overall fuel formulation which complies with regulatory standards (for example, EN 228 for European automotive gasoline fuels) and is therefore suitable for use in unmodified vehicle engines.
Consequently, there remains a need for high alternative and biofuel content fuels that comply with the existing specifications for unleaded gasoline. It is an aim of the present invention to provide alternative gasoline fuel formulations that contain higher proportions of alternative and/or biofuel components than are presently feasible and yet are still able to meet current or future fuel specifications and engine requirements.